Update README and fix default docker image command

Dockerfile.goreleaser

@@ -8,4 +8,3 @@ COPY http-echo /http-echo
 USER nonroot:nonroot
 
 ENTRYPOINT ["/http-echo"]
-CMD ["--help"]

README.md

@@ -1,12 +1,24 @@
 # http-echo
 
-Forked from <https://github.com/hashicorp/http-echo>
-
 =========
 
 HTTP Echo is a small go web server that serves the contents it was started with
 as an HTML page.
 
+## Install
+
+### Homebrew
+
+```bash
+brew install verifa/tap/http-echo
+```
+
+### Docker
+
+```bash
+docker run verifa/http-echo -env ECHO_TEXT='hello world!'
+```
+
 The default port is 5678, but this is configurable via the `-listen` flag or `ECHO_TEXT` environment variable:
 
 ```bash
@@ -18,3 +30,7 @@ ECHO_TEXT="hello world" http-echo -listen=:8080
 ```
 
 Then visit <http://localhost:8080/> in your browser.
+
+=========
+
+Forked from <https://github.com/hashicorp/http-echo>